Various treatments for a variety of medical conditions involve the transfer of exogenous genetic information into cells of a patient or a cell donor. For example, CAR-T (chimeric antigen receptor T cell) technology involves taking blood samples from a patient and processing those cells in a manner that returns genetically engineered populations of T cells to the patient's body once they have been programmed to recognize specific antigens on targeted cells. Typically, genes are transferred into T cells by viral transduction with a retrovirus (e.g., lentivirus), but they can also be transfected into cells using physical methods such as electroporation or cell constriction within channels, chemical methods, or other approaches.